21CT55 #2628 restoration

[Zenith6S321]

Before I did the color alignment I wanted to try to lower the flyback drive current as much as I could without messing up the width, linearity, or adding visible drive lines. I tried making the HOT drive DC voltage more negative by increasing the grid to ground resistance, but too much adds drive lines. I found the HOT screen voltage was high, so I changed the 10K screen resistor to 11K and ended up adding 2.2K to that and just barely have enough width with the width switch set to max. I only got it down to around 200 mA without getting visible problems. I also messed with the 7.5 ohm silicon diode dropping resistor. I ended up with a 4 ohm dropping resistor to get right at 400VDC with my AC input voltage. To make checking voltages and currents easier later, I added a terminal strip on the transformer side of the selenium rectifier tower with low ohm resistors in series with the supply voltage rails so I can check voltage and current on the four rails. I also added a terminal strip to the back of the HV cage with a jumper to insert a current meter in the HOT cathode and a 10 ohm resistor in series with the HV regulator cathode to measure its current. With the chassis back in the set I did another horizontal and vertical alignment and ended up with 25KV HV, 205-200 mA HOT current, full vertical and full horizontal deflection with decent linearity. With the color oscillator now running I can see that the color is not locked.